DOHA, March 27 (Reuters) - Qatar announced contracts worth about $23 billion on Thursday to buy attack helicopters, guided missiles, tankers and other weapons from Boeing Co, Airbus and other arms makers as the Gulf state accelerates its military build-up.

The world's top liquefied natural gas (LNG) exporter announced deals with about 20 global companies, including firms from the United States which were awarded deals worth 27.5 billion riyals ($7.6 billion), said a spokeswoman for a Doha defense conference where the announcements were made.

The weapons purchases include large deals with Lockheed Martin, Raytheon and others.

Qatar, and other Gulf Arab and Middle Eastern countries are looking to acquire new high-tech military equipment to protect themselves from neighboring Iran and internal threats after the Arab Spring uprising.

Boeing confirmed that the announcement included a contract to buy 24 AH-64E Apache attack helicopters and three Boeing 737 Airborne early warning and control (AEW&C) aircraft.

The deal for the helicopters was valued at 8.9 billion riyals, said the spokeswoman for the conference.

In Paris, France's Defense Ministry said Qatar had agreed to buy 22 NH90 military helicopters from a unit of European aerospace group Airbus worth 2 billion euros ($2.76 billion) and two Airbus-made refueling tankers.

Qatar also committed to buy a Patriot missile defense system built by Raytheon equipped with PAC-3 missiles made by Lockheed; advanced daytime, high-definition sensors and radars for Apache helicopters; and Javelin missiles built by a Lockheed-Raytheon joint venture, according to sources familiar with the matter.

Raytheon had told analysts in January that it expected to finalize an order with Qatar in the first half of 2014 for over $2 billion in Patriot missile defense system equipment.

The Pentagon approved the sale to Qatar of $9.9 billion worth of Patriot fire units, radars, and various Raytheon and Lockheed missiles in November 2012.

The Defense Security Cooperation Agency, the U.S. body which oversees foreign arms sales, had notified lawmakers in July 2012 of a possible sale of Apache helicopters to Qatar.

A spokeswoman for the U.S. agency had no immediate comment.

Washington has been keen to deepen its cooperation with Gulf nations, which have been long-standing allies, on missile defense and increase pressure on Iran over its nuclear program.

The Apache helicopters are built by Boeing and used by the U.S. Army, Egypt, Greece, Israel, Japan, Kuwait, Netherlands, Saudi Arabia, Singapore, the United Arab Emirates, and United Kingdom.

They will be fitted with Longbow radar equipment made by a joint venture of Lockheed and Northrop Grumman Corp.